Accurate electronic identification of objects moving through an area is highly desirable. Electronic identification systems eliminate the need for visual monitoring of the objects by a person. Therefore, a greater volume of moving objects may move through the area of interest and still be detected. Further, because electronic identification systems can be adjusted to respond quickly to moving objects, the speed of movement of the moving objects may be increased without the electronic identification system losing the ability to identify the objects.
In the dairy industry such an electronic system is particularly useful. On a dairy farm a limited number of persons operate a milking parlor and many cows enter the parlor for milking in a short time. It is critical to know which cow is approaching the milking apparatus for milking, as the dairy farmer needs to be able to monitor, and also record, the daily milk output for each cow. Without a fast and accurate electronic identification systm, the milking parlor operator would have to visually identify each cow, thus causing extensive time delays in the milking procedure.
Prior attempts to electronically identify farm animals include U.S. Pat. to Carroll No. 4,475,481, issued Oct. 9, 1984, where a passive transponder device containing a coil is hung on a chain or rope around the animal's neck. For identifying an animal which is feeding, the '481 patent apparatus provides an identifier in the feeder box. The identifier has a coil driven by a power amplifier for transmitting energy to the coil in the transponder. The energized transponder then generates an RF signal containing unique identifying information relating to that animal. This signal containing identifying information is transmitted back to the identifier where it is decoded and sent to a computer, which then directs an auger in the feeder box to dispense the proper amount of feed for that particular animal.
A significant problem with the '481 patent apparatus is that the electromagnetic field generated by the identifier, which is used to energize the transponder, is oriented in only one direction, and therefore, if the animal turns his or her head 90.degree., the axis of the coil in the transponder becomes perpendicular to the axis of the coil in the identifier, and there is insufficient magnetic coupling between the identifier and the transponder, resulting in a failure to energize the transponder and a consequent inability to identify the animal based on transponder-transmitted information.
The Carroll '481 apparatus also does not provide any separate means for sensing the presence of the animal in the feeder (apart from the transponder signal) or for sensing the direction of movement of the animal. Such information is of value as a check on the accuracy of any detection based on the presence of a transponder signal and allows for greater control and monitoring ability of a procedure involving a large number of moving objects, such as cows moving through a milking parlor.